Indicate
by check mark whether the registrants: (1) have filed all reports required to be
filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the
preceding 12 months (or for such shorter period that the registrant was required
to file such reports), and (2) have been subject to such filing
require­ments for the past 90
days. Yes (X)
No ( )

Indicate by check mark whether each
registrant is a large accelerated filer, an accelerated filer, a non-accelerated
filer or a smaller reporting company. See definitions of “accelerated filer,”
“large accelerated filer” and “smaller reporting company” in Rule 12b-2 of the
Securities Exchange Act of 1934.

Large
Accelerated Filer

Accelerated

Filer

Non-Accelerated
Filer

Smaller
Reporting

Company

Ameren
Corporation

(X)

(
)

(
)

(
)

Union
Electric Company

( )

(
)

(X)

(
)

Central
Illinois Public Service Company

( )

(
)

(X)

( )

Ameren
Energy Generating Company

( )

(
)

(X)

(
)

CILCORP
Inc.

( )

(
)

(X)

(
)

Central
Illinois Light Company

( )

(
)

(X)

(
)

Illinois
Power Company

( )

(
)

(X)

(
)

Indicate by check mark whether each
registrant is a shell company (as defined in Rule 12b-2 of the Securities
Exchange Act of 1934).

Ameren
Corporation

Yes

(
)

No

(X)

Union
Electric Company

Yes

(
)

No

(X)

Central
Illinois Public Service Company

Yes

(
)

No

(X)

Ameren
Energy Generating Company

Yes

(
)

No

(X)

CILCORP
Inc.

Yes

(
)

No

(X)

Central
Illinois Light Company

Yes

(
)

No

(X)

Illinois
Power Company

Yes

( )

No

(X)

The
number of shares outstanding of each registrant’s classes of common stock as of
April 30, 2008, was as follows:

Ameren
Corporation

Common
stock, $.01 par value per share – 209,474,844

Union
Electric Company

Common
stock, $5 par value per share, held by Ameren

Corporation
(parent company of the registrant) – 102,123,834

Central
Illinois Public Service Company

Common
stock, no par value, held by Ameren

Corporation
(parent company of the registrant) – 25,452,373

Ameren
Energy Generating Company

Common
stock, no par value, held by Ameren Energy

Resources
Company, LLC (parent company of the

registrant
and subsidiary of Ameren

Corporation)
– 2,000

CILCORP
Inc.

Common
stock, no par value, held by Ameren

Corporation
(parent company of the registrant) – 1,000

Central
Illinois Light Company

Common
stock, no par value, held by CILCORP Inc.

(parent
company of the registrant and subsidiary of

Ameren
Corporation) – 13,563,871

Illinois
Power Company

Common
stock, no par value, held by Ameren

Corporation
(parent company of the registrant) – 23,000,000

OMISSION
OF CERTAIN INFORMATION

Ameren
Energy Generating Company and CILCORP Inc. meet the conditions set forth in
General Instruction H(1)(a) and (b) of Form 10-Q and are therefore filing this
form with the reduced disclosure format allowed under that General
Instruction.

This
combined Form 10-Q is separately filed by Ameren Corporation, Union Electric
Company, Central Illinois Public Service Company, Ameren Energy Generating
Company, CILCORP Inc., Central Illinois Light Company, and Illinois Power
Company. Each registrant hereto is filing on its own behalf all of the
information contained in this quarterly report that relates to such registrant.
Each registrant hereto is not filing any information that does not relate to
such registrant, and therefore makes no representation as to any such
information.

TABLE
OF CONTENTS

Page

GLOSSARY
OF TERMS AND
ABBREVIATIONS.....................................................................................................................................................................................................

Statement
of
Income.......................................................................................................................................................................................................................................

Item
2. Unregistered Sales of Equity Securities and Use of
Proceeds.................................................................................................................................................................

This Form
10-Q contains “forward-looking” statements within the meaning of Section 21E of
the Securities Exchange Act of 1934, as amended. Forward-looking statements
should be read with the cautionary statements and important factors included on
page 7 of this Form 10-Q under the heading “Forward-looking Statements.”
Forward-looking statements are all statements other than statements of
historical fact, including those statements that are identified by the use of
the words “anticipates,” “estimates,” “expects,” “intends,” “plans,” “predicts,”
“projects,” and similar expressions.

4

GLOSSARY
OF TERMS AND ABBREVIATIONS

We use
the words “our,” “we” or “us” with respect to certain information that relates
to all Ameren Companies, as defined below. When appropriate, subsidiaries of
Ameren are named specifically as we discuss their various business
activities.

AFS –
Ameren Energy Fuels and Services Company, a Resources Company subsidiary that
procures fuel and natural gas and manages the related risks for the Ameren
Companies.

Ameren –
Ameren Corporation and its subsidiaries on a consolidated basis. In references
to financing activities, acquisition activities, or liquidity arrangements,
Ameren is defined as Ameren Corporation, the parent.

Ameren Services
–Ameren
Services Company, an Ameren Corporation subsidiary that provides support
services to Ameren and its subsidiaries.

ARO –
Asset retirement obligations.

Baseload
– The minimum
amount of electric power delivered or required over a given period of time at a
steady rate.

Capacity
factor – A percentage measure that indicates how much of an electric
power generating unit’s capacity was used during a specific period.

CILCO –
Central Illinois Light Company, a CILCORP subsidiary that operates a
rate-regulated electric and natural gas transmission and distribution business
and a non-rate-regulated electric generation business through AERG, all in
Illinois, as AmerenCILCO. CILCO owns all of the common stock of
AERG.

CILCORP –
CILCORP Inc., an Ameren Corporation subsidiary that operates as a holding
company for CILCO and various non-rate-regulated subsidiaries.

CIPS –
Central Illinois Public Service Company, an Ameren Corporation subsidiary that
operates a rate-regulated electric and natural gas transmission and distribution
business in Illinois as AmerenCIPS.

Development
Company – Ameren Energy Development Company, which was an Ameren Energy
Resources Company subsidiary, and parent of Genco, Marketing Company, AFS, and
Medina Valley. It was eliminated in an internal reorganization in February
2008.

GAAP –
Generally accepted accounting principles in the United States of
America.

Genco –
Ameren Energy Generating Company, a Resources Company subsidiary that operates a
non-rate-regulated electric generation business in Illinois and
Missouri.

Gigawatthour
– One thousand megawatthours.

Heating
degree-days – The summation of negative differences between the mean
daily temperature and a 65- degree Fahrenheit base. This statistic is useful as
an indicator of demand for electricity and natural gas for winter space heating
for residential and commercial customers.

ICC –
Illinois Commerce Commission, a state agency that regulates the Illinois utility
businesses and the rate-regulated operations of CIPS, CILCO and IP.

Illinois Customer
Choice Law – Illinois Electric Service Customer Choice and Rate Relief
Law of 1997, which

5

provided
for electric utility restructuring and introduced competition into the retail
supply of electric energy in Illinois.

Illinois electric
settlement agreement – A comprehensive settlement of issues in Illinois
arising out of the end of ten years of frozen electric rates, as of January 2,
2007. The Illinois electric settlement agreement, which became effective on
August 28, 2007, was designed to avoid new rate rollback and freeze legislation
and legislation that would impose a tax on electric generation in Illinois. The
settlement addresses the issue of future power procurement, and it includes a
comprehensive rate relief and customer assistance program.

IP SPT –
Illinois Power Special Purpose Trust, which was created as a subsidiary of IP
LLC to issue TFNs as allowed under the Illinois Customer Choice Law. IP SPT is a
variable-interest entity, as the equity investment is not sufficient to permit
IP SPT to finance its activities without additional subordinated
debt.

IPA –
Illinois Power Agency, a state government agency that has broad authority to
assist in the procurement of electric power for residential and nonresidential
customers beginning in June 2009.

Kilowatthour
–A
measure of electricity consumption equivalent to the use of 1,000 watts of power
over a period of one hour.

Marketing Company
–Ameren
Energy Marketing Company, a Resources Company subsidiary that markets power for
Genco, AERG and EEI.

Money pool
–Borrowing
agreements among Ameren and its subsidiaries to coordinate and provide for
certain short-term cash and working capital requirements. Separate money pools
maintained for rate-regulated and non-rate-regulated business are referred to as
the utility money pool and the non-state-regulated subsidiary money pool,
respectively.

Moody’s
–Moody’s
Investors Service Inc., a credit rating agency.

MoPSC –
Missouri Public Service Commission, a state agency that regulates the Missouri
utility business and operations of UE.

PGA –
Purchased Gas Adjustment tariffs, which allow the passing through of the actual
cost of natural gas to utility customers.

PUHCA 2005
– The Public Utility Holding Company Act of 2005, enacted as part of the Energy
Policy Act of 2005, effective February 8, 2006.

Regulatory
lag – Adjustments to retail electric and natural gas rates are based on
historic cost levels and rate increase requests can take up to 11 months to be
granted by the MoPSC and the ICC. As a result, revenue increases authorized by
regulators will lag behind changing costs.

Resources Company
– Ameren Energy Resources Company, LLC, an Ameren Corporation subsidiary
that consists of non-rate-regulated operations, including Genco, Marketing
Company, EEI, AFS, and Medina Valley. It is the successor to Ameren Energy
Resources Company, which was eliminated in an internal reorganization in
February 2008.

RTO –
Regional Transmission Organization.

S&P –
Standard & Poor’s Ratings Services, a credit rating agency that is a
division of The McGraw-Hill Companies, Inc.

SEC –
Securities and Exchange Commission, a U.S. government agency.

SFAS
–Statement
of Financial Accounting Standards, the accounting and financial reporting rules
issued by the FASB.

SO2
–Sulfur
dioxide.

TFN –
Transitional Funding Trust Notes issued by IP SPT as allowed under the Illinois
Customer Choice Law. IP must designate a portion of cash received from customer
billings to pay the TFNs. The proceeds received by IP are remitted to IP SPT.
The proceeds are restricted for the sole purpose of making payments of principal
and interest on, and paying other fees and expenses related to, the TFNs. Since
the application of FIN 46R, IP does not consolidate IP SPT. Therefore, the
obligation to IP SPT appears on IP’s balance sheet.

natural gas transmission and
distribution business in Missouri as AmerenUE.

FORWARD-LOOKING
STATEMENTS

Statements
in this report not based on historical facts are considered “forward-looking”
and, accordingly, involve risks and uncertainties that could cause actual
results to differ materially from those discussed. Although such forward-looking
statements have been made in good faith and are based on reasonable assumptions,
there is no assurance that the expected results will be achieved. These
statements include (without limitation) statements as to future expectations,
beliefs, plans, strategies, objectives, events, conditions, and financial
performance. In connection with the “safe harbor” provi­sions of the Private
Securities Litigation Reform Act of 1995, we are providing this cautionary
statement to identify important factors that could cause actual results to
differ materially from those anticipated. The following factors, in addition to
those discussed under Risk Factors and elsewhere in this report and in our other
filings with the SEC, could cause actual results to differ materially from
management expectations suggested in such
forward-looking statements:

·

regulatory
or legislative actions, including changes in regulatory policies and
ratemaking determinations, such as the outcome of pending UE, CIPS, CILCO
and IP rate proceedings or future legislative actions that seek to limit
or reverse rate increases;

·

uncertainty
as to the effect of implementation of the Illinois electric settlement
agreement on Ameren, the Ameren Illinois Utilities, Genco and AERG,
including implementation of a new power procurement process in Illinois
that began in 2008;

·

changes
in laws and other governmental actions, including monetary and fiscal
policies;

·

changes
in laws or regulations that adversely affect the ability of electric
distribution companies and other purchasers of wholesale electricity to
pay their suppliers, including UE and Marketing
Company;

·

enactment
of legislation taxing electric generators, in Illinois or
elsewhere;

·

the
effects of increased competition in the future due to, among other things,
deregulation of certain aspects of our business at both the state and
federal levels, and the implementation of deregulation, such as occurred
when the electric rate freeze and power supply contracts expired in
Illinois at the end of 2006;

·

the
effects of participation in the
MISO;

·

the
availability of fuel such as coal, natural gas, and enriched uranium used
to produce electricity; the availability of purchased power and natural
gas for distribution; and the level and volatility of future market prices
for such commodities, including the ability to recover the costs for such
commodities;

·

the
effectiveness of our risk management strategies and the use of financial
and derivative instruments;

·

prices
for power in the Midwest, including forward
prices;

·

business
and economic conditions, including their impact on interest
rates;

·

disruptions
of the capital markets or other events that make the Ameren Companies’
access to necessary capital more difficult or
costly;

·

the
impact of the adoption of new accounting standards and the application of
appropriate technical accounting rules and
guidance;

·

actions
of credit rating agencies and the effects of such
actions;

·

weather
conditions and other natural
phenomena;

·

the
impact of system outages caused by severe weather conditions or other
events;

operation
of UE’s nuclear power facility, including planned and unplanned outages,
and decommissioning costs;

·

the
effects of strategic initiatives, including acquisitions and
divestitures;

·

the
impact of current environmental regulations on utilities and power
generating companies and the expectation that more stringent requirements,
including those related to greenhouse gases, will be introduced over time,
which could have a negative financial
effect;

the
inability of our counterparties and affiliates to meet their obligations
with respect to contracts and financial
instruments;

·

the
cost and availability of transmission capacity for the energy generated by
the Ameren Companies’ facilities or required to satisfy energy sales made
by the Ameren Companies;

·

legal
and administrative proceedings; and

·

acts
of sabotage, war, terrorism or intentionally disruptive
acts.

7

Given
these uncertainties, undue reliance should not be placed on these
forward-looking statements. Except to the extent required by the federal
securities laws, we undertake no obligation to update or revise publicly any
forward-looking statements to reflect new information or future
events.

8

PART
I. FINANCIAL INFORMATION

ITEM
1. FINANCIAL STATEMENTS.

AMEREN
CORPORATION

CONSOLIDATED
STATEMENT OF INCOME

(Unaudited)
(In millions, except per share amounts)

Three
Months Ended

March
31,

2008

2007

Operating
Revenues:

Electric

$

1,467

$

1,463

Gas

612

561

Total
operating revenues

2,079

2,024

Operating
Expenses:

Fuel

302

263

Purchased
power

287

373

Gas
purchased for resale

459

421

Other
operations and maintenance

423

389

Depreciation
and amortization

176

183

Taxes
other than income taxes

113

102

Total
operating expenses

1,760

1,731

Operating
Income

319

293

Other
Income and Expenses:

Miscellaneous
income

21

16

Miscellaneous
expense

(4

)

(5

)

Total
other income

17

11

Interest
Charges

100

100

Income
Before Income Taxes, Minority Interest, and

Preferred
Dividends of Subsidiaries

236

204

Income
Taxes

87

71

Income
Before Minority Interest and Preferred Dividends of
Subsidiaries

149

133

Minority
Interest and Preferred Dividends of Subsidiaries

11

10

Net
Income

$

138

$

123

Earnings
per Common Share – Basic and Diluted

$

0.66

$

0.59

Dividends
per Common Share

$

0.635

$

0.635

Average
Common Shares Outstanding

208.7

206.6

The
accompanying notes are an integral part of these consolidated financial
statements.

9

AMEREN
CORPORATION

CONSOLIDATED
BALANCE SHEET

(Unaudited)
(In millions, except per share amounts)

March
31,

December
31,

2008

2007

ASSETS

Current
Assets:

Cash
and cash equivalents

$

186

$

355

Accounts
receivable – trade (less allowance for doubtful

accounts
of $38 and $22, respectively)

656

570

Unbilled
revenue

318

359

Miscellaneous
accounts and notes receivable

315

280

Materials
and supplies

556

735

Other
current assets

272

181

Total
current assets

2,303

2,480

Property
and Plant, Net

15,294

15,069

Investments
and Other Assets:

Nuclear
decommissioning trust fund

291

307

Goodwill

831

831

Intangible
assets

189

198

Regulatory
assets

1,149

1,158

Other
assets

701

685

Total
investments and other assets

3,161

3,179

TOTAL
ASSETS

$

20,758

$

20,728

LIABILITIES
AND STOCKHOLDERS' EQUITY

Current
Liabilities:

Current
maturities of long-term debt

$

823

$

221

Short-term
debt

1,617

1,472

Accounts
and wages payable

443

687

Taxes
accrued

88

84

Other
current liabilities

539

438

Total
current liabilities

3,510

2,902

Long-term
Debt, Net

5,066

5,691

Preferred
Stock of Subsidiary Subject to Mandatory Redemption

16

16

Deferred
Credits and Other Liabilities:

Accumulated
deferred income taxes, net

1,989

2,046

Accumulated
deferred investment tax credits

106

109

Regulatory
liabilities

1,328

1,240

Asset
retirement obligations

569

562

Accrued
pension and other postretirement benefits

856

839

Other
deferred credits and liabilities

346

354

Total
deferred credits and other liabilities

5,194

5,150

Preferred
Stock of Subsidiaries Not Subject to Mandatory Redemption

195

195

Minority
Interest in Consolidated Subsidiaries

23

22

Commitments
and Contingencies (Notes 2, 8, 9, and 10)

Stockholders'
Equity:

Common
stock, $.01 par value, 400.0 shares authorized –

shares
outstanding of 209.4 and 208.3, respectively

2

2

Other
paid-in capital, principally premium on common stock

4,656

4,604

Retained
earnings

2,115

2,110

Accumulated
other comprehensive income (loss)

(19

)

36

Total
stockholders’ equity

6,754

6,752

TOTAL
LIABILITIES AND STOCKHOLDERS' EQUITY

$

20,758

$

20,728

The accompanying notes are
an integral part of these consolidated financial statements.

10

AMEREN
CORPORATION

CONSOLIDATED
STATEMENT OF CASH FLOWS

(Unaudited)
(In millions)

Three
Months Ended

March
31,

2008

2007

Cash
Flows From Operating Activities:

Net
income

$

138

$

123

Adjustments
to reconcile net income to net cash

provided
by operating activities:

Gain
on sales of emission allowances

(2

)

(4

)

Mark-to-market
(gain) loss on derivatives

(16

)

4

Depreciation
and amortization

180

182

Amortization
of nuclear fuel

11

9

Amortization
of debt issuance costs and premium/discounts

5

5

Deferred
income taxes and investment tax credits, net

23

(12

)

Minority
interest

8

7

Other

(1

)

6

Changes
in assets and liabilities:

Receivables

(78

)

(193

)

Materials
and supplies

179

158

Accounts
and wages payable

(106

)

(81

)

Taxes
accrued

4

77

Assets,
other

(25

)

19

Liabilities,
other

(16

)

37

Pension
and other postretirement benefit obligations

22

21

Net
cash provided by operating activities

326

358

Cash
Flows From Investing Activities:

Capital
expenditures

(420

)

(357

)

Nuclear
fuel expenditures

(102

)

(23

)

Purchases
of securities – nuclear decommissioning trust fund

(89

)

(47

)

Sales
of securities – nuclear decommissioning trust fund

86

43

Purchases
of emission allowances

(2

)

(5

)

Sales
of emission allowances

-

2

Other

-

1

Net
cash used in investing activities

(527

)

(386

)

Cash
Flows From Financing Activities:

Dividends
on common stock

(133

)

(131

)

Short-term
debt, net

145

341

Dividends
paid to minority interest holder

(7

)

(5

)

Redemptions,
repurchases, and maturities:

Long-term
debt

(19

)

(174

)

Issuances:

Common
stock

46

21

Net
cash provided by financing activities

32

52

Net
change in cash and cash equivalents

(169

)

24

Cash
and cash equivalents at beginning of year

355

137

Cash
and cash equivalents at end of period

$

186

$

161

The accompanying notes
are an integral part of these consolidated financial statements.

11

UNION
ELECTRIC COMPANY

CONSOLIDATED
STATEMENT OF INCOME

(Unaudited)
(In millions)

Three
Months Ended

March
31,

2008

2007

Operating
Revenues:

Electric
– excluding off-system

$

490

$

451

Electric
– off-system

151

122

Gas

83

76

Other

-

1

Total
operating revenues

724

650

Operating
Expenses:

Fuel

147

125

Purchased
power

53

40

Gas
purchased for resale

55

49

Other
operations and maintenance

217

224

Depreciation
and amortization

81

87

Taxes
other than income taxes

60

57

Total
operating expenses

613

582

Operating
Income

111

68

Other
Income and Expenses:

Miscellaneous
income

14

10

Miscellaneous
expense

(2

)

(2

)

Total
other income

12

8

Interest
Charges

41

48

Income
Before Income Taxes and Equity

in
Income of Unconsolidated Investment

82

28

Income
Taxes

29

9

Income
Before Equity in Income

of
Unconsolidated Investment

53

19

Equity
in Income of Unconsolidated Investment,

Net
of Taxes

11

14

Net
Income

64

33

Preferred
Stock Dividends

1

1

Net
Income Available to Common Stockholder

$

63

$

32

The
accompanying notes as they relate to UE are an integral part of these
consolidated financial statements.